Oil return mechanism for refrigeration systems



R. H. SWART Oct. 21, 1952 OIL RETURN MECHANISM FOR REFRIGERATION SYSTEMS Filed Dec. 15. 1948 FIG.|

IN VEN TOR. #M Q Patented Oct. 21, 1952 Richard H. Swart, Syracuse, N. Y., assignor'to Carrier Corporation, Syracuse, N. Y., a corporation of Delaware Application December 15, 1948, Serial No.f65,48t

{This invention relates to refrigeration systems and more particularly to a refrigeration system including economical'and efficient means for returning "oil dissolved in the refrigerant to the compressor While restricting or blocking free flow of liquid refrigerant from the evaporator to the compressor.

In the operation of the usual type refrigeration system, the compressor lubricant tends to mix "with therefrigerant thru oil pumping by the compressor pistons or byudirect transfer of oil foam f-rom'the' compressor crankcase thru the intake ports of the compressor and from thence into the refrigerant circuit. Such lubricant in solution with'the' refrigerant. liquid reduces the efficiencyof the heat'transfer surfaces and also decreases the' quantity of oil lubricant in the compressor crankcase. It is necessary-that some means be provided to return this lubricant to the compressor crankcase. In refrigerant systems having-"continuous evaporator tubing without any traps or accumulators, the lubricant is returned to the compressor with the refrigerant vapor which moves at high velocities. In a large majority of refrigerating systems, it is necessary to include a trap or accumulator as part or all of the system. In this type of system, the lubricant being non-volatile, tends to remain in the trap especially in systems where undersome conditionsof operation the trap" is not supplied with liquid refrigerant. If. no means are provided to return the contents of thetrap to the crankcase of the compressor, lubrication failure of the compressor may ensue. "Heretofore, means proposed to return this lubricant to the compressor were liable to' return unevaporated liquid refrigerant to the crankcase of the compressor which caused damage to working parts of the compressor or impaired the lubricating qualities of the lubricant.

The chief object of the present invention is to provide means in a refrigeration system for separating oil from liquid refrigerant, returning the oil to the compressor while preventing return of liquid refrigerant.

An object of the present invention is to provide a refrigeration system including an accumulator which will serve as a reservoir for liquid refrigerant but which will not accumulate oil. A further object is to provide a refrigeration system in which an accumulator is connected to the suction line of the system whereby passage of gaseous fluid in the suction line reduces oil collected in the accumulator to return to the compressor, the connection being so designed that I 2 Claims. (c1. 62-11175) free flow of liquid refrigerant thereinis restricted by "vaporization thereof, the bubbles serving to block the outlet "of the accumulator preventing or retarding free flow "of refrigerant therethrough. .Other objects of my invention will be readily perceived from the'followi ng description.

This invention relates to a refrigeration system including a compressor, a condenser,an expansion device and an evaporator connected by the suction line to the'compres'sor'. An accumulator is disposed in the suction line but serves as a reservoir for liquid refrigerant. Oil also collects to some extent in the accumulator. The bottom of the accumulator is connected'to the suction line by a conduit of small diameter. 'The outlet in the accumulator is also of small dialriieter. At least a portion of the conduit extends downward below the accumulator and such downward extension portion is exposed to ambient atmosphere Wherebyits temperature is higher than the temperature in the accumulator. Passage of gaseous refrigerant in the suction line induces oil collected in the accumulator through the conduit and returns the oil'to the compressor. However, if no oil is present inthe accumulator, liquid refrigerant mayattempt to return to the-compressor which would be unentering the conduit is vaporized, the bubbles of.-v

gaseous refrigerant rising in the conduit to restrict free flow of liquid refrigerant therein and serves to block free flow of liquid refrigerant into the conduit.

The attached drawing illustrates a preferred embodiment of my invention, in which Figure 1 is a diagrammatic view of a refrigeration system including the present invention; and

Figure 2 is an exaggerated sectional view disclosing the construction of the accumulator and connecting conduit.

Referring to the drawing, there is shown a refrigeration system including a compressor 2 connected to condenser 3 by discharge line 4. Condenser 3 is connected to an evaporator 5 by liquid line 6. A suitable expansion device I such as a capillary tube or a thermal expansion valve is disposed in line 6 to regulate the refrigerant flowing to the evaporator 5. A suction line 8 connects the evaporator 5 and compressor 2. An accumulator 9 is disposed in the suction line 8 and acts as a reservoir for liquid refrigerant preventing such refrigerant flooding into the compressor and also serves to collect oil passing through the refrigeration system. The accumulator 9 is inclined downward to some extent to assure that liquid therein collects in a pool at one end ID; the suction line connections are made to the raised end of the accumulator.

At end- :Nl lat-accumulator '9,:an outlet H of small diameter is provided connected to a conduit l2. Conduit l2 includes a downward extending portion 13 and a second portion I4 which connects, as shown in Figure 2, with suction line 8. The passage of gaseous refrigerantsthrough the suction line serves to induce oil collected in the accumulator to enter. thesuctionline and to return such oil together withsgaseousrrefriger ant to the compressor.

When all oil collected in the accumulator 9 has been withdrawn it will be appreciated any liquid refrigerant collected therein will attemptito pass through the conduit [2,finduced by the passage .of gaseous refrigerant :insuction line 8. Conduit -..|2v isrexposed to ambientatmosphere so thatthe temperature thereof is higher than the tempera- :turein accumulator.9. The outlet H :beingof .small. diameterit will -be appreciatedany liquid refrigerant passing therethrough flashes to some extent. The heat transferred to the conduit portion 13 from the ambient atmosphere .andoutlet .ll cooperate -.to vaporizeor produce a smallseries of :bubbles 15' which serve to restrict free flow .of liquid refrigerant in the conduit. Suchbub- .bles .I 5 rise upward in the conduit portion 13 and .aid in blocking .outlet H .to prevent to someextent passage of .liquid refrigerant .therethrough.

.Any refrigerant ableto .seep through the barriers -so provided is ingaseousform when itis drawn .into thesuctionline .8 since portion 1-4 of conduit .1 2 is .also exposed :to .theambient atmosphere.

...If it be desired toincrease the formation of bubbles l5 at the accumulator outlet H, fins 16 .orsimilar heat concentrating means may be disposed about conduit portion l3. Any suitable means of increasing the temperature of such conduitportion may be utilized.

It will .be understood the invention so disclosed -.is.also applicable 'toa-refrigeration system employing a flooded type evaporator in which the accumulator is integral with the evaporator.

My invention provides a simple and economical means of assuring that oil carried through the refrigeration. system is returned to the com- ;pressor. In addition, such means prevents liquid refrigerant being drawn .into...the compressor i-fromthe accumulator which mayresult in "seriof a compressor, a condenser, an expansion device and an evaporator, a suction line connect- .iing' the evaporator and the compressor, an accumulat'or adapted to receive oil and refrigerant from. the evaporator, and means for returning oil collected in the accumulator, said means including an outlet in the accumulator of relatively small diameter, and a conduit of relatively small diameter connecting the outlet to the suction :line, said conduit :havinga portion :extending -downwardfrom the accumulator andexposedto ambient atmosphere to cause liquid refrigerant .to vaporize therein, the vaporized u-refrigera-nt flowing upward toxrestrict the accumulator outlet, oil returning from the accumulator through the :conduit to the suction line; the outlet :and the conduit .being so constructednand'arran ed that IiquidJrefrigerant in the downward ext-end- .ing'portionof the conduit is vaporized producing a .series of bubbles which flow upwardintothe accumulator to -:restrict. the outlet thereby blocking ifreei how of liquid refrigerant ithroughvth'e outlet; :and means tov increase the temperature of .the downward portion cof. the rconduit.

2.. A refrigeration system according to claim 11 :in whichthe. temperature increasing means :comprise metal fins disposed about "the :exteriorz of the :downwardextending conduit portion.

RICHARD H: SWART.

, ,R'EFERENGES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,899,378 'Zou'ck Feb.1:28, 1933 21343.68 :Threlkeld Nov. 1,1938

. FOREIGNPATENTS Number Country Date 192,664 a Switzerland...--. -..Aug.,31,.;l937 

